CAT 3 Wiring for a Wall Jack

Old 09-21-12, 06:12 AM
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CAT 3 Wiring for a Wall Jack

I have CAT 3 wiring run in my house and I'm trying to add a wall jack to add internet service that we just started. I realized that the wall jack we have wasn't wired. So, I Googled and searched this forum but all the diagrams and instructions reference a CAT 3 wire colors that are different than what I find my wire. I don't know if it fairly old CAT 3 wiring or what but here are the wire colors, but I'm really confused what color wire goes were on a phone jack. From what i googled, it sounds like this is fairly typically. Here are my wire colors and let me know if you have any thoughts on where they connect!

1. Solid Orange
2. Orange and White
3. Solid Red
4. Solid Blue (fairly light blue)
5. Blue and White
6. Solid Green
7. Green and White
8. Solid Grey
9. Grey and White
10. Brown and White
11. Blue and Red
Old 09-21-12, 07:56 AM
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You only need two wires for the jack. Color isn't that important. You should have pairs of wires twisted together. Using the two wires in a twisted pair is what is important. Find an unused twisted pair and use that. Blue/blue-white would normally be line one and Orange/Orange-white would normally be line 2. Traditional untwisted pair would be
line1-red and green line2 black and yellow.
Old 09-21-12, 08:17 AM
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This color combination is not common, you will probably find them twisted 2 by 2, or 4 by 4.
The total of 11 conductors leave one for e.g. grounding. They will probably be togeter like this:
Blue Blue and White
Orange-Orange and White
Green-Green and White
Red-Blue and Red
Grey-Grey and White
Brown and White

It is not of great importance witch pairs you use, but test if it is in use already.

The twisting is made to reduce noise, so it is smart to keep the pairs.

Old 09-21-12, 09:04 AM
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Thanks for the info. Well, I thought it would be a simple DIY project but then noticed the colors. The cable must be an older CAT 3 because the colors aren't normal but also the wires aren't twisted in pairs as you mentioned. In looking around the internet for answers, it seems the twisted pairs is not as normal in the CAT 3 world. I thought it was already in use but wasn't working and when I pulled the cover, I notice it wasn't wired at all. The CAT 3 cable was cut at the floor. I assume the previous owner was starting it and didn't finish. So, I should just use 2 pairs (4 wires) total? Does it matter which pins (the screws in the jack) the pairs are connected to? Out of curiosity, what are the other wires used for?
Old 09-21-12, 09:27 AM
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Is this the same line as other phones in your house? If so, look at how one of those jacks is connected.
Old 09-23-12, 08:54 PM
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It's odd to find in residential, but what you have is called 'trunk cable'. It's not technically cat3, because the wire pairs aren't twisted - they are just colored in pairs for identification. (Cat 3 cables do use twisted pairs, but the twist is much looser than you would see in a Cat 5 cable). Trunk cable used to be common in old office buildings that used the 5 line desk phones with the light up buttons to select the line.

That was the cable they used to connect each phone to the PBX computer. There were 5 pairs for the actual lines (usually it was 4 outside lines plus an 'extension number' for in-house calling), and one pair for the ringer which was controlled by the computer. The reason the ringer was controlled separately by the computer is because if you were on the phone you didn't want it ringing full blast in your ear - so the computer (which could tell whether you were on the phone) either kept the ringer silent and just flashed the light on the button, or rang it softly.

Imagine one floor of an office building with 50 cubicles, each cubicle has one of those cables going to it. Then there's the private offices and such which also have phones.. Now imagine there's a bunch of floors.. And all that wiring from all the phones on all the floors goes into a big closet where it connects to huge wiring blocks and from the wiring blocks it connects to a computer or several computers.. I've been in a few of them.. They can get really gnarly after a while from people changing things and adding things.

So now you know what that cable is really used for..

In your case it was most likely just what the installer had left on the truck when your house was wired back in the day. If you strip it further back there will be a twelfth wire in there somewhere. It would be white with brown. And there was no solid red in there, the solid red one will have a blue stripe on it further down - it pairs with the blue/red one. There was no odd number of wires or ground on this type of cable. It only came in 2, 4, 6, 12, 25, 50, and 100 pair sizes.

Now.. That said, what do you mean by adding a jack for the internet? Is this DSL? If so, your speeds will suffer dearly using that cable. You need to make a new run of Cat 5 from that jack to where the phone lines come in on the side of the house. Cat5 can be used for phone and is recommended for phone lines that carry DSL signals because as DSK mentioned above, it helps reduce the noise on the line. Noise affects your DSL speeds.

Now if you are trying to use this jack as a network jack to bring the internet from your router to another computer, it definitely won't work..

Last edited by JerseyMatt; 09-23-12 at 09:24 PM.
Old 09-24-12, 08:12 AM
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Thanks for all the input. I never had phone service in my house and I only had 2 phone jacks in the house. My house is a 1939 house and there was a wall mounted jack that didn't work, after checking the wiring on it, it looked like it might have been original phone line connection and it was cut off in basement. We had another "modern" jack in a bedroom but like I described it earlier, it wasn't connected. It was just stubbed up from the floor into the jack so I didn't have any working phone jacks to look for a solutions. I used Ray2047's comment and wired a phone jack to receive my "Cat-3" wire. It worked! All the colors wired that differed from the typical CAT 3 really confused me. ATT, who is providing our internet service, provided a DSL converter for the phone line and a wireless hub. From what I read, I may go back and rerun CAT 5 cables just to ensure the fastest speeds. Thanks for all the help!

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